FR2693231A1 - Cooling device for a motor vehicle engine - Google Patents

Abstract

The invention relates to a cooling device for a motor vehicle engine. The device comprises a heat exchanger (14) adapted to be traversed by a cooling fluid and to be swept by an air flow, at least one means (26, 30) for controlling the flow rate of the air flow sweeping the heat exchanger, this control means having several different states, first sensor means (50) suitable for providing a first digital quantity representative of the speed of the vehicle, second sensor means (44, 46, 48) suitable for providing a second digital quantity representative of the flow rate of the cooling fluid passing through the heat exchanger and control means (CMD) of said control means as a function of the first and second quantities, these control means operating according to two different functions, depending on whether the flow rate of coolant is decreasing or increasing. Application to motor vehicles.

Description

Cooling device for motor vehicle engine

  The invention relates to a cooling device for a

motor vehicle engine.

  Such a cooling device usually comprises a heat exchanger, called a cooling radiator, adapted to be traversed by a cooling fluid, usually water with an antifreeze, and to be swept by an air flow, and that at least one means for controlling the flow of air flowing through the heat exchanger, this means of

  control having several different states.

  In the usual way, this control means is constituted by a fan with several states of speed, capable of modifying the

  flow of the air flow through the heat exchanger.

  As another means of control, it is also sometimes used a set of pivoting flaps that can be placed in different opening positions to change the air flow through the heat exchanger, while influencing the coefficient of

  aerodynamic penetration of the motor vehicle.

  In all cases, the control means makes it possible to modify the flow rate of the air flow which sweeps the heat exchanger and which, in the absence of such a control means, would be due to the sweeping

  natural air, which depends on the speed of the vehicle.

  Conventionally, the states of the airflow flow control means are controlled via an element

  sensitive to the temperature of the coolant passing through

heat exchanger.

  We realized that taking into account this alone

  parameter, that is the temperature of the cooling fluid.

  is not sufficient because it does not always make it possible to anticipate the complex phenomena which are at the origin of

  temperature variations of the coolant.

  To overcome this drawback, the Applicant has recently proposed to also take into account other parameters, including the speed of the vehicle and the flow rate of the cooling fluid through the heat exchanger However, the practical embodiment of such a device cooling

  poses a number of difficulties.

  The invention makes it possible precisely to solve these difficulties by proposing a cooling device of a new type suitable for taking into account other parameters than the only temperature parameter which is traditionally used for

control of the control means.

  The invention relates more particularly to a device for

  cooling for a motor vehicle engine, comprising

  nant: a heat exchanger suitable for being traversed by a cooling fluid and to be swept by an air flow, at least one means for controlling the flow of air flowing sweeping the heat exchanger, this control means having a plurality of different states, first sensor means capable of providing a first digital quantity, representative of the vehicle speed, filtered on average in the short term, second sensor means capable of supplying a second digital quantity, representative of the flow rate of the cooling fluid traveling through the heat exchanger, and means for controlling said control means according to

first and second sizes.

  According to an essential characteristic of the invention, these control means operate according to two different functions,

  depending on whether the coolant flow rate is decreasing

or increase.

  Thus, the control means of the flow control means of the air flow operate taking into account the action of the fluid of

  cooling, whose flow is decreasing or increasing

  through the heat exchanger, and the efficiency of this heat exchanger which depends on the speed of the motor vehicle It follows that, these control means thus allow to act, in an anticipated manner; on the command of the means of

flow control of the air flow.

  This results in better coordination of the action of the control means, especially for low speeds of the motor vehicle, when the natural sweep of the air is insufficient

  to ensure proper cooling of the motor.

  In one embodiment of the invention, the control means comprise first electronic means capable of defining a first multi-state control according to a first function, on the one hand, of the position of the first magnitude in a predetermined sequence of ranges. adjacent filtered speed, secondly of the second magnitude, second electronic means, adapted to define a second multi-state control according to a second function on the one hand

  the position of the first magnitude in a predetermined sequence.

  of the second magnitude, said control means actuating either the first electronic means, by controlling the state of said air flow rate control means according to the first command multi-state, the second electronic control means, by controlling the state of said flow control means

  of air according to the second multi-state control.

  Thus, the control means operate in function, firstly, of the position of the first quantity (representative of the speed of the vehicle), in a predetermined sequence of predetermined ranges of filtered speed, previously defined, and secondly , of the second magnitude (representative of the flow of

  cooling fluid flowing through the heat exchanger).

  According to another characteristic of the invention, each of the first and second functions comprises comparing the second magnitude with a threshold which depends on the position of the first magnitude in said predetermined sequence of adjacent speed ranges, and the choice, depending on whether the second quantity (representative of the flow rate of the cooling fluid) is less than or greater than the threshold, between a control state corresponding at most to the maintenance, or to the acceleration of the

air flow.

  Thus, for each of the speed ranges considered, each

  first and second functions compare the magnitude

  flow rate at a predetermined threshold.

  In a preferred embodiment of the invention, the first and second electronic means comprise two tables defining two respective laws for the state of the first and second commands as a function of values of the second

magnitude, and speed ranges.

  We can thus define two different laws, depending on whether the flow

  of coolant-is decreasing or increasing

tion.

  In one embodiment of the invention, each of the first and second controls is capable of four different states corresponding to maximum airflow, average airflow, minimum airflow, and unchanged airflow.

  different are chosen for each particular case.

  Thus, in the case where the flow rate of the cooling fluid is increasing, it can be provided that each of the first and second controls is capable of the following states: minimum air flow rate for a fast speed of the vehicle, unchanged air flow or maximum for average vehicle speeds, average or maximum airflow for low vehicle speed. In the same example, in the case where the flow rate of the cooling fluid is decreasing, it can be provided that each of the first and second controls is capable of the following states: minimum air flow for a fast speed of the vehicle, flow of minimum or unchanged air for average vehicle speeds, unchanged airflow or medium for low vehicle speed. Advantageously, the second quantity takes into account the current value of the flow rate of cooling fluid as well as

of its previous value.

  This second magnitude can be constituted by any magnitude representative of the flow rate of the cooling fluid flowing

the heat exchanger.

  In one embodiment of the invention, this second magnitude is provided by a pair of values, one of which is the supply voltage of an electric pump ensuring the circulation of the cooling fluid in the heat exchanger, and the other is related to the position of a valve regulating the flow of coolant in

the heat exchanger.

  For each pair of these two values, there is a well-defined value of the coolant flow rate. According to the invention, the airflow flow control means is constituted by a fan having several different speed states and / or by a set of shutters.

  having several different opening states.

  In the description that follows, made only as an example,

  Referring to the accompanying drawings, in which: Figure 1 is a diagram of an engine provided with a cooling device according to the invention;

  FIG. 2 is an operating flowchart of the device

  tif of the invention; Figure 3 is a graph showing a defined number of values representative of the flow rate of the coolant; Figure 4 is a flowchart of the control means of the device of the invention; Fig. 5 is a three-dimensional graph showing the states of the first electronic means as a function of four adjacent ranges of rate and range of flow; Figure 6 is a table defining the law of the first control means; FIG. 7 is a three-dimensional diagram showing the states of the second electronic means as a function of the same speed ranges and the same flow rate ranges as in the case of FIG. 5; and FIG. 8 represents a table defining the law of

  second electronic means of FIG. 7.

  Referring first to Figure 1 which shows an internal combustion engine 10 of a motor vehicle, provided with a cooling circuit The engine 10 is cooled by a cooling fluid, for example water added to antifreeze, which leaves the motor 10 = through an outlet duct 12, then travels through a main heat exchanger 14 (called cooling radiator) and then returns to the engine via an inlet duct 16 The circulation of the cooling fluid is carried out at by means of a pump 18 driven by an electric motor 20, the speed of which varies as a function of the electrical voltage applied to it. Thus, the flow rate of the cooling fluid regulated by the pump 18 is independent of the

speed of rotation of the engine 10.

  On the outlet duct 12 is mounted, immediately upstream of the heat exchanger 14, a flow metering valve, here a valve 22 of the butterfly type actuated by a geared motor 24, to modify the flow rate of the cooling fluid.

  traversing the heat exchanger 14.

  The heat exchanger 14 is swept by an air flow (arrows F) whose flow rate is regulated by two control means: on the one hand a fan 26 driven in rotation by an electric motor 28, and on the other hand a set of pivoting shutters 30

  similar to a Venetian blind and powered by a motorcycle

  reducer 32 The motor 28 and the geared motor 32 are driven

by CMD control means.

  The fan has three different speed states zero speed, low speed and high speed The flaps 30 can also take a finite number of different states of

  the full state closes when fully open.

  The cooling circuit further comprises a bypass duct 34 connecting the ducts 12 and 16, and on which is mounted a secondary heat exchanger 36 serving as a radiator

  cabin heater and expansion vessel 38.

  The engine 10 comprises an intake manifold 40 connected to a bypass duct 42 connected to the duct 16, for heating the collector. The collector 40 is provided with a

  sensor 44 providing an indication of the pressure of

engine.

  The motor 10 is further provided with a tachometer 46 giving the

  speed of rotation of the engine, expressed in revolutions per minute.

  The device further comprises a temperature sensor 48 mounted on the bypass duct 34, upstream of the secondary heat exchanger 36, and able to give an indication of the temperature entering the secondary heat exchanger.

  36, but also in the main heat exchanger 14.

  In addition, the device comprises a speed sensor 50 driven by the wheels 52 of the motor vehicle and able to provide a numerical quantity, representative of the vehicle speed, filtered on average in the short term This sensor gives an encrypted measurement according to a sequence of whole values with a step of 1 km / h, this measurement being updated periodically, for example every 1.5 s The speed value is taken in

  account by the CMD control means.

  Referring now to Figure 2 which shows an operating flowchart of the cooling device of Figure 1. The device comprises control means 54, in themselves known, actuating the pump 18 and the valve 24; and will be described in detail later The device further comprises control means CMD for operating the fan 26 and the pivoting flaps 30, that is to say the control means of

  flow of the air flow sweeping the heat exchanger 14.

  The pressure sensor 44 provides a pressure value (in k Pa) representing the engine intake pressure, while the counter 46 gives the engine rotation speed in revolutions per minute (TPM) from a pressure diagram. engine intake (k Pa) / engine speed (TPM) can calculate the engine load by calculation means 56 and determine two operating zones, a first low-load zone o the coolant temperature must not exceed a certain threshold, in example 115 C, and a second zone corresponding to the maximum load of the engine, in which the temperature of the cooling fluid must not exceed another threshold, in the example 1000 C By means of calculation 58, it is thus determined which of the two temperature thresholds

  corresponds to the measurements delivered by the sensors 44 and 46.

  The temperature measurement provided by the sensor 48 and giving the value of the temperature of the fluid at the inlet of the heat exchanger 14 is compared with the temperature threshold provided by the means 58. the

  control means 54 the valve 24 and the pump 18.

  In practice, at a given temperature supplied by the sensor 48, there corresponds a pair of values: on the one hand the position of the valve 24 and on the other hand the electrical supply voltage of the

  electric motor 20 of the pump 18.

  These pairs of values, which may be called "steps", are in the example to the number of 12, each step being designated by an index of 0 to 11 For each of these 12 indices corresponds to a given value of the flow in the heat exchanger 14, as

shown in Figure 3.

  This figure shows, by way of example, the value of the flow rate of the cooling fluid (expressed in liters per hour) as a function of the index of the corresponding step. Thus, for the index O corresponds to a flow rate of O l / h, for index 1 a flow rate of 130 l / h, for index 2 a flow rate of 200 l / h, etc. and

  for the index 11, a flow rate of 3750 l / h.

  Thus, by the means defined above, it is possible to provide a numerical quantity representative of the flow rate of the cooling fluid flowing through the heat exchanger. In the example, these are twelve flow rate values as defined in FIG.

  As will be seen below, this numerical quantity, representing

  the flow rate of the cooling fluid flowing through the heat exchanger, could be another quantity, for example a quantity directly linked to the supply voltage of the pump 18, if no valve was provided.

in the circuit.

  We will now describe the CMD control means of the invention

  using Figure 2 and Figures 4 to 8.

  The control means CMD actuate the fan 26 and the flaps 30 from first sensor means (sensor 50)

  to provide a first digital magnitude Gi, representing

  the vehicle speed, f iltrated on average in the short term, and second sensor means (sensor 60) adapted to provide a second digital magnitude G 2, representative of the flow rate of the cooling fluid flowing through the heat exchanger. In the example (FIG. 2), the second sensor means 60

  include all the sensors 44, 46 and 48.

  However, as already indicated, all

  another means of providing a numerical quantity

  the flow rate of the cooling fluid flowing through the sample.

heateur 14.

  According to the invention, the CMD control means operate according to two different functions, depending on whether the flow of fluid

  cooling is decreasing or increasing.

  For this, the control means comprise (FIG. 4): there are first electronic means able to define a first multi-state control CMD 1 according to a first function, on the one hand, of the position of the first variable Gi in a predetermined sequence of adjacent beaches of filtered speed, secondly of the second magnitude G 2, second electronic means, able to define a second multi-state control CMD 2 according to a second function on the one hand the position of the first magnitude Gi in the predetermined sequence of adjacent filtered speed ranges, and

  on the other hand, of the second magnitude G 2.

  Said control means actuate either the first electronic means, by controlling the state of the airflow control means (in the example the fan 26) according to the first multi-state control CMD 1, or the second means control electronics, by controlling the state of said airflow control means in accordance with the second

multi-state control.

  The first and second electronic means comprise two tables TAB 1 and TAB 2 defining two respective laws for the state of the first and the second command as a function of

  the value of the second magnitude, and velocity ranges.

  The first electronic means operate when the flow rate of cooling fluid is increasing, and that according to a law whose table is represented in two ways

  different in Figures 5 and 6.

  FIG. 5 represents a three-dimensional diagram showing four speed ranges: Vi (speed of 0-19 km / h), V 2 (speed of 20-49 km / h), V 3 (speed of 50-89 km / h) and V 4

(speed above 90 km / h).

  The diagram also shows eleven indices (numbered from 0 to 10) related to the flow of cooling fluid flowing

the heat exchanger 14.

  In the example, each index corresponds to a pair of two

  consecutive stage indices of Figure 3.

  Thus, the index O corresponds to the pair 0,1 of FIG. 3, the index 1 to the pair 1,2 of FIG. 3, etc. and the index 10 to

the pair 10,11 of FIG.

  The diagram of FIG. 5 also shows four states A, B, C, D corresponding to four states respectively.

  different from the first order.

  State A corresponds to a minimum airflow (zero fan speed), state B to an unchanged state, state C to medium airflow (fan setting to low speed), and state D at maximum airflow (fan setting on

high speed).

  Figure 6 shows, in tabular form, the diagram in three

dimensions of Figure 5.

  The function of the first electronic control means comprises comparing the second magnitude G 2 with a threshold which depends on the position of the first magnitude Gi in the predetermined sequence of adjacent speed ranges, that is to say of the four ranges. V1 to V4, and the choice, depending on whether the second magnitude G 2 is less than or greater than the threshold, between a control state corresponding at most to the maintenance, or to

the acceleration of the air flow.

  Thus, when the value Gi is in the range Vi (0-19 km / h), the law requires that for the indices O and 1 (low flow) the fan is in the state C (low speed) When the flow increases and as soon as the threshold corresponding to index 3 is reached, the law requires that the fan be in

  state D, that is to say that it rotates at high speed.

  In the case where the magnitude Gi is in the range V 2, for the indices O to 7, the law requires that the fan is in the B state (unchanged) When the flow increases and reaches the threshold corresponding to the index 8, the fan goes to the state

  D (high fan speed).

  When the magnitude Gi is in the range V 3 (50-89 km / h), for the indices of 0 to 9, the law imposes that the fan is in the state B (unchanged) When the flow reaches the index 10, the law requires the fan to go to state D (setting to

high speed).

  When the magnitude Gi is in the range V 4 (speed greater than 90 km / h), the fan is set to state A (zero fan speed) for all the indices O to 10.

  Therefore, in the case where the flow of the cooling fluid

  The device can take the following states: minimum air flow for a fast vehicle speed (range V 3), unchanged air flow or maximum for average vehicle speeds (V 2 and V 3 ranges). ), and average or maximum air flow for a low speed of

vehicle (beach Vi).

  In the same way, it is defined, in the case where the flow rate of the cooling fluid is decreasing, another law whose table is represented in two different ways on the

Figures 7 and 8.

  FIG. 7 shows the same speed ranges VI to V 4 and the same indices O to 10 corresponding to different values.

  the flow rate of the cooling fluid.

  In the example, there are three states E, F and G E corresponds to the setting of the fan at zero speed, F to the state of passage of the fan at low speed if it is at high speed, and

state G to an unchanged state.

  When the first magnitude Gi is in the range Vl, for

  indices 10 to 4, the state of the fan is unchanged (state G).

  When the flow rate of fluid decreases and reaches the index 3, the law requires that the fan passes at low speed, if it were

  previously at high speed.

  When the magnitude Gi is in the range V 2 (20-49 km / h), for the indices 10 to 5, the law imposes that the fan is in the state G (unchanged) When the flow of fluid decreases and that we reach the index 4, the law requires that the fan goes to state E, that is to say that its speed is zero. For the V 3 and V 4 ranges, the law requires that the fan be

  found in the state E, corresponding to a zero speed.

  Thus, when the cooling fluid is decreasing, the device is capable of the following states: minimum air flow rate for a fast vehicle speed (range V 4), minimum or unchanged air flow rate for average vehicle speeds ( ranges V 3 and V 2), and minimum airflow unchanged or medium for low speed

of the vehicle (beach Vl).

  Since the second magnitude G 2 is compared with an index (0-

  10) itself consisting of a pair of indices, this second magnitude takes into account the current value of the fluid flow rate

  as well as its previous value.

  As shown in FIG. 4, the tables TAB 1 and TAB 2 each receive, on the one hand, a signal representing the value Gi, and

  on the other hand a signal representing the value G 2 after comparison

  sound with a table TAB 3 representing the indices 0-11.

  Furthermore, the magnitude G 2 is compared in electronic test means to determine whether the value of the flow rate is increasing or decreasing and to drive accordingly a switch I that makes it operational

  first command CMD 1, the second command CMD 2.

  Of course, the tables given previously in FIGS.

  to 8, are only exemplary embodiments.

  Thus the choice of speed ranges and values

  the flow rate of the coolant and the number of

  control states are subject to variations.

  As indicated, it is possible to order also the flaps 30 according to appropriate laws, the tendency being that the flaps are somewhat open when the speed of the vehicle is low and they are on the contrary somewhat closed when the speed of the vehicle is high, and this particularly

  for reasons of aerodynamic penetration.

Claims (9)

claims   1 Cooling device for a motor vehicle engine, comprising a heat exchanger (14) adapted to be traversed by a cooling fluid and to be swept by a flow of air, at least one control means (26, 30) the flow rate of the air flow sweeping the heat exchanger (14), this control means having several different states, first sensor means (50) capable of supplying a first digital quantity representative of the speed of the vehicle, filtered in short-term average, second sensor means (18,22) adapted to provide a second digital quantity, representative of the flow rate of the cooling fluid flowing through the heat exchanger (14), and control means (CMD) of said cooling means; control according to the first and second quantities, characterized in that these control means (CMD) operate according to two different functions, depending on whether the fluid flow of   cooling is decreasing or increasing.   2 Device according to claim 1, characterized in that the control means comprise first electronic means, adapted to define a first control (CMD 1) with several states according to a first function on the one hand the position of the first magnitude ( Gi) in a predetermined sequence of adjacent beaches (Vl to V 4) of filtered speed, secondly of the second magnitude (G 2), second electronic means, able to define a second command (CMD 2) with several states according to a second function on the one hand of the position of the first quantity (Gi) in the predetermined sequence of adjacent beaches (Vl to V 4) of filtered speed, on the other hand of the second quantity (G 2), said means control unit actuating either the first electronic means, controlling the state of said airflow control means in accordance with the first multi-state control, or the second electronic control means, controlling the state of udit means of airflow control according to the   second multi-state command.   3 Device according to claim 2, characterized in that   each of the first and second functions includes the comparison   its second magnitude (G 2) to a threshold which depends on the position of the first magnitude (Gi) in said predetermined sequence of adjacent ranges of velocity (V 1 -V 4), and the choice, depending on whether the second magnitude (G 2) is less than or greater than the threshold, between a control state corresponding to   more maintenance, or the acceleration of the air flow.   4 Device according to one of claims 2 and 3, characterized   in that the first and second electronic means comprise two tables (TAB 1, TAB 2) defining two respective laws for the state of the first and the second control as a function of values of the second magnitude (G 2), and of the speed ranges (Vl-V 4).   Device according to one of Claims 2 to 4, characterized   in that each of the first and second controls (CMD 1, CMD 2) is capable of four different states corresponding to maximum air flow rate, average air flow rate, minimum air flow rate and flow rate air unchanged.   6 Device according to claim 5, characterized in that, in the case where the flow rate of the cooling fluid is increasing, each of the first and second controls is capable of the following states: minimum air flow rate for a fast speed of the vehicle, Unchanged or maximum airflow for average vehicle speeds, average or maximum airflow for low vehicle speed. 7 Device according to claim 5, characterized in that, in the case where the flow rate of the cooling fluid is decreasing, each of the first and second controls is capable of the following states: minimum air flow rate for a fast speed of the vehicle, minimum or unchanged airflow for average vehicle speeds, minimum airflow unchanged or medium for low speed of the vehicle.   8 Device according to one of claims 1 to 7, characterized   in that the second magnitude (G 2) takes into account the current value of the cooling fluid flow and its previous value.   9 Device according to one of claims 1 to 8, characterized   in that the second magnitude (G 2) is provided by a pair of values, one of which is the supply voltage of an electric pump (18) for circulating the cooling fluid in the heat exchanger ( 14), and the other is related to the position of a valve (22) regulating the fluid flow   cooling in the heat exchanger.   Device according to one of Claims 1 to 9, characterized   in that the flow control means of the air flow is a   fan (26) having a plurality of different speed states.   11 Device according to one of claims 1 to 9, characterized   in that the flow control means of the air flow is a set of flaps (30) having several different opening states.